Just curious…can you tell me what happened to these two plants?
Too much rain water? or is it something else
Looking over your photos, my best guess is a combination of rain followed by the several real cold snaps we had, cause frost/freeze damage and that opened them up to infection. The Cleistocactus (the tall fuzzy one with multiple arms) looks like the damaged arm should be trimmed off with a knife and the cut part at ground level splashed with hydrogen-peroxide, so the infection stops with just that arm. Clean your knife and recut the top part above the infection so you have clean green tissue with no signs of orange and black, splash it with the peroxide, let it heal and dry for a week or two inside and replant and it may root (Cleistocactus are slow or tricky to root but in never hurts to try). I would also suggest pulling out the mammilaria and tossing it, so it does not spread the fungus infection to the other plants.
Generally those cacti are hardy here but if they are wet and then we get real frosty they can be damaged.